During the last decade, the acknowledgement for sustainability has arisen to meet the demands for then and future generations. Thereby, the attention has shifted to incorporate the civic demands into urban planning processes. By 2021, a mandatory integration of participation will be obliged from a governmental perspective due to the implementation of the new Environmental and Planning Act. Although there are many kinds of research on the theoretical part of the participation process, it is not yet clear which factors are essential for meaningful participation, while becoming socially sustainable as well. Besides, this study focuses on mixed-use (re)developments, where the configuration of actors is more diverse. Therefore, the main question of this research is: How can a meaningful public participation process be achieved in mixed-use (re)developments and thereby become socially sustainable? To answer the main question, a literature study and empirical study are conducted on participation processes in mixed-use area development. Two extremes of participation processes are selected for the case-studies: top-down and bottom-up. They give insight into the relationship between participation and social sustainability, the social relation of the affected public and the preconditions for meaningful participation in mixed-use areas. The conclusion of this study indicates factors as “observed mutual help”, “improvement of the willingness of affected public” and “transparency” as crucial elements overlapping the communicative planning approaches, preconditions and social sustainability.